Many motor tools such as engine-driven handheld cutting machines have saw blades which may be circular or ring-shaped. Such a cutting machine may be used for cutting hard materials such as concrete, where the cutting procedure may result in the creation of dust. For example concrete dust is unhealthy to breathe and also impairs visions, and it is desired to minimize the creations of such dust that freely may expand in the air. Such free concrete dust that finds its way into the engine of the tool could affect the engine in a negative way.
Many tools of the above type or for this purpose equipped with a water supply, where a flow of water is directed towards the saw blade in such a way that a large quantity of the dust is mixed with the water and thus retained and kept from expanding in the air. The flow of water is preferably held at a minimum while maintaining a proper function, since the water normally has to be taken care of at the working site, and more water than necessary is undesirable. Tools of the above type are therefore equipped with a valve which the user may operate to obtain a flow of water providing a desired effect. However, today these valves are of a relatively simple design, being either of the on/off type, or of a type with a relatively rough setting of the water flow. GB 2352997 shows a liquid dispensing system for a handheld cutting machine. It has a control valve conveniently located. But the valve handle must be turned several revolutions to adjust this throttling valve, which is awkward. Another system has a valve handle that only needs to be turned 90 degrees. But this valve has a conical inner rubber body that is turned inside a conical plastic housing. The conical shape gives an axial force. But the conical rubber body is also strongly pretensioned into the housing to make the arrangement watertight. All this creates a valve handle that is hard to turn for the user.
It is therefore desired to provide such a valve that is arranged for a smooth and stepless change of water flow which is easily manageable for a tool user.